This paper addresses the first practical application of spatial filtering techniques to data taken with a multibeam receiver. Spatial filters make use of the relative arrival times of a signal at multiple sensors to identify and separate signals from different directions. The method is a consequence of the Karhunen-Loeve theorem and relies on the eigen decomposition of the covariance matrix formed from the multiple signal paths. The effectiveness of the spatial filtering techniques is demonstrated on observations of the Vela pulsar taken with the Parkes 20 cm Multibeam receiver. The experiment was highly successful, and the results show spatial filtering methods provide powerful tools for interference mitigation with an array feed receiver. Extensions of the algorithm to reduce computational requirements and allow application on short (submillisecond) timescales are also explored.